Proposed model for miR-449/miR-34 to act through E2F-pRb pathway in control of male germ cell development during murine testicular development and spermatogenesis. In this model, CREMτ and SOX5 activate the expression of miR-449 upon meiotic initiation. miR-449 in collaboration with miR-34b/c then suppresses the expression of factors that belong to the E2F-pRb pathway, including CDK4/6, CCND1, CDK25A, MYC, and E2F1/2/3/5. These changes further cause reduced levels of E2F proteins and an increase in hypophosphorylated pRb protein level, which will further reduce E2F activities and thus affect male germ cell development during both the meiotic and haploid phases of spermatogenesis.